Electric circuit breakers



E. COLEMAN ELECTRIC CIRCUIT BREAKERS Dec.- 23, 1958 4 Sheets-Sheet 1Filed Nov. 50, 1955 E. COLEMAN ELECTRIC CIRCUIT BREAKERS Dec. 23, 1958 4Sheets-Sheet 4 Filed Nov. 30, 1955 United States Patent Dfifice2,866,036 ELECTRIC CIRCUIT BREAKERS Edward Coleman, Crabtree & C0.company Application November 30', 1955, Serial No. 550,132

Claims priority, application Great Britain December 15, 1954 17 Claims.(Cl. 200-116) Walsall, England, assignor to J. A. Limited, Walsall,England, a British may be associated with a magnetic arrangement foractui aling the mechanism instantly on short circuit conditions.Alternatively the overload device may be an armature which is flexedmagnetically so as to be instantaneously attracted on overload, or shortcircuit, for actuating the trip mechanism. The principal object of theinvention is to provide a small and compact construction in which therisk of flash-over between the contacts is eliminated or minimized, andin which a very rapid break is obtained on a predetermined overload orshort circuit. A further object is to reduce friction and wear andthereby minimize the effort required for actuation of the trip mechanismby the overload device. A further object is to produce an ethcientarrangement in which the latched engagement between a trip lever andsuch device is desirably small and constant for different currentadjustments. Yet another object is to provide a simple means forindicating the condition of the circuit breaker and to enable thecurrent required for tripping to be adjusted reliably and simply by saidmeans which avoid the necessity for mznipulation of the bimetal or ofmeans which cause its position to be varied.

According to one feature of the invention an insulating plate carryingthe moving contact has pivotal engagement with a trip lever and isadapted to isolate opposed chambers inwhich the fixed contactsaremounted, for the purpose of preventing flash-over between them.

A further feature of the invention is to provide a longitudinallydivided or bifurcated flexing member having one leg disposed parallel toa current-carrying strip so that a magnetic field is induced foractuating the tripping mechanism. The flexing current-carrying memberforactuating the trip' mechanism may be connected in series with a metalstrip spaced therefrom and adapted for carrying current in the samedirection so that the flexing member is actuated instantaneously onoverload when the member is an armature and also on short circuit whensuch memher is a bimetal.

Another feature of the invention is to maintain the flexing member inengagement with. an abutment inthe casing bya spring, the tension orcompression of which'is adjustable so that the current required fortrippingmay'be varied Without any alteration in the degree of latchedengagement of the member with a trip lever.

According toa further feature of the invention theinsulating platecarrying" the moving contacts is, on a predetermined overload, initiallymoved freely through a gap into abutment with" a fulcrum before"finallydisengag'ing the moving contact'fromthefixedcontacts. Sucharrangement develops a kinetic energy or impetus which resultsineffectively overcoming inertia in'tliemoving contact a'nd in breakingdown any'incipie'nt welding of the contacts.

The circuit breaker may be operated by a dolly' having 2,866,036Patented Dec. 23, 1958 a cam surface operable on the insulating platethrough a guidingly mounted pin or roller eng'ageable with a slope orramp on the plate.- The casing may comprise moulded casing parts theopposed walls of which are formed with grooves and with recesses orchambers for the reception or the pivot pins, rollers, contacts andother components of the circuit breaker; Such parts may also be formedwith ribs or baffies for providing tortuous paths for contributing tothe dissipation of the energy of the arc in its passage from the contactchambers. Thelatter separated, by the said insulating plate, may havethe arcs deflected laterally, by the provision of shaped insulatingpartitions, into expansion chambers, from which the gases are dischargedthrough louvre outlets in the casing parts. Thus the heat energy of thearcs is effectively absorbed before discharge of the gases.

In order to enable the invention to be readily understoodreference willnow be made to the accompanying drawings illustrating by way of examplea circuit breaker embodying a flexing member in the form of a bimetalplate, in which drawings:

Figure 1 is a perspective view to an enlarged scale, with one side ofthe moulded casing removed and showing the parts in the on position.

Figure 2 is a side elevation of Figure 1.

Figure 3 is a section on the line III-III of Figure 2'.

Figure 4 is a section on the line IV-IV of Figure 2.

Figures 5, 6 and 7 are views similar to Figure 2 Figure 5 illustratingthe parts in the tripped position, Figure 6 showing the parts in the ofland reset positions, and Figure 7 showing the parts in the positionbetween those illustrated in Figures 5 and 6.

Figure 8 is a perspective view to an enlarged scale of the bimetal andassociated parts.

Referring to the drawings each member 1, 2 of a twopart moulded casinghas its-opposed faces recessed or chambered, for the receptionof thecomponents of the circuit breaker. The members 1, 2 are connected byrivets 1a and provided at top and bottom with terminals 3, 4. The upperterminal 3 is disposed on the exposed upper end of a metal strip" 5provided on its lower end with one of a pair of fixci contacts 7, 7adisposed in the front of a rectangular chamber 8of the casing. The otherfixed contact 7a is mounted on one end of a re'arwardly extending strip9, the other end of which is secured by screws 10 to the free end of onearm 11 of a bifurcated bimetal plate mounted in opposed grooves at therear of the casing parts. The free end of the other arm 11a of thebimetal is secured by screws 10a to a strip 6' of extended length. Theend of this strip is formed with a right-angled bend, the exposed lowerarm of which has the terminal 4 mounted thereon. The length of the stripis so bent that the major portion is parallel to, and disposed just outof contact with, the rear of the first-mew tioned arm 11 of the bimetal,so that a space 60' is provided between these parts. Such arrangementresults in all of the current flowing through said arm andthe strip inthe same direction. The induced magnetic field causes flexing of thebimetal atitsunited end and rapidly actuates the tripping mechanism. Theimproved arrangement enables a highly eflicient tripping on shortcircuit conditions to be achieved practically entirely due to magneticattrac tion between the two series connected, current carrying stripsproducing instantaneous flexing ofthe member 11, without the aid ofwound-magnets.

The united end of the U-shaped bimetal is free t'oflex and one leg isformed with an inwardly projecting lug 11b engaged by the end of apivotally'mountedtrip lever 12'. A helical'tension spring 13 has one endengaged with the" bimetal. and serves for pressing the free end againstan abutment 14 on the casing. The degree of pressure with which thebimetal is pressed against this abutment may be varied by the adjustmentof a screw 15, the head of which is accessible for rotation from thefront of the casing and the other end of which enters a tapped openingin an L-shaped bracket 16 secured to the other end of the screw. Thearrangement enables the latch engagement between the trip lever 12 andthe bimetal 11 to be desirably small and constant for all positions ofscrew adjustment. This adjustment affects the tension of the spring andconsequently the pressure with which the bimetal is pressed against theabutment 14, thereby resulting in more or less heating of the bimetalbeing required. for producing tripping of the contacts. The requisitecurrent for effecting tripping may be observed on a scale marking on thecasing cooperating with the screw. Instead of a tension spring, acompression spring may be provided which is operative on the rear faceof the bimetal.

The trip lever comprises two parallel plates 18, 18a, one of which isformed with a rearwardly extending leg 12 engageable with the bimetal.The lever is pivoted between its ends, on a fixed transverse pin 17, andthe plates are formed with slots 19, at right-angles to the length ofthe leg 12 for freely receiving a pin 20 carried on the lower end of afiat insulating plate 21. This plate, disposed between the mouldedcasing parts 1, 2, has its upper end of enlarged area and formed with asmall aperture 21a through which extends a closely fitting transversecontact strip 22 having contact buttons 23a at each end for engagementwith the fixed contacts 7, 7a. The provision of the moving contacts oneach side of the insulating plate results in the isolation of thecontact chambers from each other so that flash-over between the contactstherein is effectively prevented.

Midway between its ends, the fiat plate 21 is pivotally connected by apin 23 to a small U-shaped member 24 on the rear end of which bears ahelical compression spring 25, which isseated at its other end in arecess 25a in the casing. The ends of the pin 23 are located in guidinggrooves 26, in the opposed faces of the casing parts 1, 2. In the onposition the spring acts for pressing the plate 21 forwardly about thepin 20 so that the moving contacts are engaged with the fixed contactsas seen in Fi ure 2.

The dolly 27, made of insulating material, is disposed between themoulded casing parts 1, 2 and has a handle portion projecting forwardlytherefrom. A semi-circular body portion 27a, through the centre of whichextends a pivot pin 28, has its rear face formed as a cam 29 which isoperative on .a metal pin 30, the ends of which are disposed in shorthorizontal guiding grooves 30a in the opposed inner faces of the casingparts 1, 2. This pin 30 is located between the cam of the dolly and aninclined ramp or slope 21b on the insulating plate 21. Such arrangementprovides a positive drive for the contacts so that interruption of thecircuit is not dependent on the action of the spring.

In operation, manual switching from the on to the off position iseffected by the dolly, the cam of which causes the roller 30 to act onthe plate 21 for turning it about the pivot 20 against the action of thespring for causing disengagement of the contacts, as shown in Figure 6.Movement of the dolly to the on position permits the compressive effectof the spring 25 to return the parts to the on position shown in Figure2, in which the roller 30 is disposed in a V-shaped formation or fulcrumon the cam. During the manual operation, the triplever 12 is locked inengagement with the bimetal 11. The movement of the pin 30 over thecrest of the cam 29 defines the respective positions of the dolly.

In the event of overload conditions, rearward flexing of the lower endof the bimetal causes release of the trip lever. A spring 31 turns thelever about its pivot 17 tothe position shown in Figure 5. As a resultthe pin 23 at the lower end of the plate 21 is moved forward by thespring 25. The front edge of the plate is thereby caused to abut againsta fixed pin 32 which then constitutes the.

till

fulcrum for the turning of the plate to bring it into the trippedposition Figure 5, and the contacts are rapidly disengaged. An abutment33 on the casing restricts the turning of the plate. During thismovement a spring 34 turns the dolly into a mid-position, in which Onand Off legends thereon are obstructed by the casing parts. In thepositions shown in Figures 2 and 6 the appropriate legend is visible.

In order to reset the circuit breaker after a tripping operation, thedolly is depressed from the position shown in Figure 5 to that shown inFigure 6, Figure 7 illustrating an intermediate position. As will beseen the trip lever is thereby turned about the pin 17 to cause itsre-engagement with the bimetal and restoration of the parts to the offposition, after which the dolly can be manipulated to bring them to theon position.

A pair of shaped insulating shields 35 disposed on each side of thespring 25 serve for deflecting the arcs from the contacts 7 and 7a intoseparate channels, each of which is formed with projecting bafiles orribs 36 arranged for constraining the arc to follow a tortuous path.Beyond the battles or ribs the gases are directed into expansionchambers 37, from which they are expelled through louvre openings 38 inside walls of the casing.

The forms of the invention here described and illustrated are presentedmerely as examples of how the invention may be embodied and applied.Other forms, embodiments and applications of the invention, comingwithin the proper scope of the appended claims, will, of course, suggestthemselves to those skilled in the art.

Having thus described our invention we claim:

1. An electric circuit breaker comprising a casing, a pair of fixedcontacts disposed therein, a bimetal element connected to said fixedcontacts, a handle mounted on such casing, a fiat insulating platedisposed longitudinally of said casing and extending between said fixedcontacts, a mounting disposed between the ends of said casing forpivotally supporting said plate, an aperture in one end of said plate, aclosely fitting moving contact bridge member extending through saidaperture and engageable at each end with said fixed contacts, apivotally mounted trip lever adapted to be actuated by said element andpivotally engageable with the other end of said plate.

2. An electric circuit breaker comprising a casing, fixed contactsmounted in said casing, an insulating plate provided with movingcontacts thereon for engagement with said fixed contacts, a terminalconnected to one of said fixed contacts, a strip for mounting said otherfixed contact, a bifurcated bimetal element, one arm of said elementsecured to said strip, a second extended strip secured to the free endof the other bimetal arm, said second strip having a bent portiondisposed parallel to said first bimetal arm and provided with a secondterminal disposed at its end.

3. An' electric circuit breaker having a casing, an abutment on saidcasing, an overload device comprising a bimetal strip having a free end,an adjustable spring acting on said free end for normally maintainingsaid strip in engagement with said abutment, the tension of said springadapted to vary the current controlling the flexing of said strip, alever in latched engagement with said strip, and means for adjusting thetension of said spring to trip said lever without altering the amount ofsuch latched engagement.

4. An electric circuit breaker comprising an overload device, a pair ofterminals, a flexing bimetallic currentcarrying member, a metal stripdisposed in spaced relation to said member and arranged to carry currentin the same direction therewith, said member and said strip connected inseries carrying the entire current passing between said terminals, and atrip mechanism adapted to be actuated by said member.

5. An electric circuit breaker according to claim I having a fulcrumabuting said insulating plate when the latter is moved freely by apredetermined overload before said plate finally disengages said movingcontacts from said fixed contacts.

6. An electric circuit breaker according to claim 2 having a pivotallymounted trip lever adapted to be activated by the united end of saidbimetal element.

7. An electric circuit breaker according to claim 2 wherein said rigidstrips connect said external terminals with respective ends of saidbimetal flexing element.

8. An electric circuit breaker according to claim 3 in which a helicaltension spring connects said armature with a bracket, and a screwengageable with said bracket adjusts the tension of said spring.

9. An electric circuit breaker according to claim 1 wherein a bracket isconnected to said insulating plate and pivotally mounted on a pin, guidegrooves in said casing for mounting said pin and spring means normallyurging said plate into contact position.

10. An electric circuit breaker comprising a casing, terminals at topand bottom of said casing, a bifurcated strip adapted to be flexed onoverload, a rigid plate connecting said strip and one of said terminalsand disposed parallel to and spaced from said strip so that currentflows through said strip and plate in the same direction, a trip leverone end of which is engageable with the united flexing end of saidstrip, a spring pressed insulating plate pivotally engageable with theother end of said lever, moving contacts on each side of said plate,fixed contacts mounted in said casing, a dolly pivotally mounted in saidcasing provided with a cam, and a roller disposed between said cam andthe front edge of said insulating plate.

11. An electric circuit breaker comprising a casing, fixed contactsdisposed therein, an insulating plate having a transversely extendingbridge member provided with moving contacts at one end thereof, a triplever engaging the other end of said plate, a pivot connecting saidlever and said plate, a dolly for actuating said plate, said platerevolving about said pivot during manual operation of said dolly, athermal bimetal strip connected to said fixed contacts engaging saidlever and adapted to be flexed on overload to release said lever, afulcrum disposed on said casing engageable by said plate in trippedposition and a spring disposed between said casing and said plateturning said plate about said fulcrum to disengage said fixed and movingcontacts.

12. An electric circuit breaker comprising a casing, an abutment on saidcasing, fixed contacts within said casing, a longitudinal insulatingplate carrying moving contacts thereon, manual means for operating saidplate, a thermal bimetal overload strip fixed to said casing at one endand 6 one free end adapted to flex on overload, a spring operable uponsaid free end for engagement with said abutment, a trip lever engageablewith said free end and adjustable means for varying the pressure saidfree end bears against said abutment.

13. An electric circuit breaker comprising a casing, fixed contacts, aflexing overload device connected to said fixed contacts, a trip leveractuated by said device, an insulating plate having pivotal engagementat one end with said lever, an arm extending transversely through theother end of said plate, contacts mounted on each end of said arm, adolly formed with a cam, a roller interposed between said cam and thefront edge of the plate, and a spring mounted in the casing and actingon the rear edge of said plate.

14. An electric circuit breaker according to claim 11 in which saidlever is L-shaped, having one arm engageable with said bimetal strip andthe other arm slotted for freely receiving said pivot.

15. An electric circuit breaker according to claim 11 in which saidlever comprises a pair of spaced plates having aligned slots, one ofsaid lever plates extending for latching engagement with said bimetalstrip.

16. An electric circuit breaker according to claim 11 having a roller,short guiding grooves provided in said casing for mounting the ends ofsaid roller, a ramp provided on said insulating plate engaging saidroller and a cam on said dolly operative on said roller.

17. An electric circuit breaker according to claim 11 wherein saidcasing is provided with contact chambers, separate lateral channels, anexpansion chamber, openings in the side walls of said casing and a pairof insulating shields, whereby arcs from said contact chambers aredefiected by said shields into said channels to said expansion chamberand expelled through said openings.

References Cited in the file of this patent UNITED STATES PATENTSGermany June 25, 1930

